The present invention relates to a method of modifying thermoplastic materials and products thereof.
A wide variety of polymers and resins of either natural or synthetic origin are available at the present time. Each of these materials possesses its own peculiar properties which make it useful for various purposes and for the production of various products. However, there are certain end uses and products made from polymers and resins which desirably possess the properties of more than one polymer or resin. Certain properties can be added to the inherent properties of the polymer or resin by a wide variety of techniques. However, all such known techniques have one or more disadvantages. Properties of two or more polymers or resins can be obtained by blending or "alloying" two or more polymers or resins. However, in such instances, such blending often masks or destroys one or more desirable inherent properties in the process of attaining an additional property not inherent in the original materials. In addition, it is often quite an expensive proposition to blend several resins simply to attain one additional property because of the added cost of the additional resin and the processing to incorporate the additional resin. Additional properties can be added to the inherent properties of a polymer or resin by the use of a variety of additives. Here again, essentially the same problems are encountered as in the blending of polymers or resins to the extent that the additives often mask or destroy certain inherent properties of the polymer or resin and add to the cost because of the cost of the additive itself and the incorporation thereof in the polymer or resin. One obvious way of combining the properties of two or more resins or polymers, particularly where only the surface properties of one of the materials is to be altered, is by laminating two or more different polymers or resins. It would also appear obvious that two different thermoplastic polymers or resins could be readily laminated by simply applying heat and pressure. However, because of the widely varying properties of polymers and resins including even those which are thermoplastic, such simplistic solutions do not often exist. Consequently in order to laminate different polymers and resins it is necessary to resort to a variety of procedures all of which add to the expense because of additional steps, additional materials, etc. and in many cases alter the physical properties which one desires to retain. For example, in many cases it is necessary to utilize an adhesive in order to obtain an adequate bond between two different resins. In still other cases the polymer or resin itself is modified to make it compatible or to permit bonding by the application of heat and pressure alone. In still other cases a vulcanizing agent, such as sulfur, is utilized between the two materials and heat and pressure are applied in order to vulcanize the materials and thus produce an adequate bond. Obviously, all of these procedures have disadvantages, not the least of which are the additional processing time, the additional processing steps and the additional materials required.
For example, rubbers and elastomers of either natural or synthetic origin possess highly desirable properties which make them useful for an extremely large number of end uses and products. Obviously, resiliency is a primary desirable property. However, appearance (usually a dull rather than shiny appearance), the feel or nonskid surface properties which can be impacted, as well as other physical properties are also quite important in certain end uses. However, rubbers and elastomers also have a number of deficiencies which limit their usefulness. For example, one significant drawback of many rubbers and elastomers is that they are not resistant to chemicals, particularly oils, greases, organic solvents and the like. In addition, rubbers and elastomers usually are not ozone, ultraviolet or weather resistant. While these properties can be imparted to rubbers and elastomers by blending various polymers or resins therewith, or the use of additives, such an approach has been found to be quite expensive, and more complex than is justified by demand for the additional property.
By contrast, thermoplastic polyalkenes do possess many of the above mentioned properties which are not generally possessed by rubbers and elastomers. Specifically, polyalkenes generally are chemical resistant, particularly resistant to oil and grease. As a matter of fact, such polyalkenes are often superior to the so-called oil resistant rubber compounds (based on nitrile rubber, chloroprene, etc.) since the latter will always absorb some oil into the surface thus making cleaning difficult even in cases where the removal of ordinary dirt is involved. By contrast the slick, nonporous, nonchemical-absorbing polyalkene surfaces are very easy to clean. Also, the addition of materials such as carbon black to polyalkenes will render the polyalkene ozone, ultraviolet light and weather resistant. However, the very property which makes polyalkenes desirable from the standpoint of chemical resistance, namely the slick, nonporous surface, makes it undesirable for many uses since such a surface is often slippery and a shiny appearance is not desired at times.
It would therefore be ideal if the desirable properties of thermoplastic polyalkenes could be combined with the desirable properties of rubber and elastomers without materially altering the properties of the rubber or elastomer and doing so in a simple and effective way. However, to date, methods of combining thermoplastic alkenes with rubbers or elastomers leave much to be desired. For example, the usual use of adhesives and vulcanization has heretofore been suggested. In addition it has also been suggested that specific elastomers, namely, hydrogenated block copolymers of high molecular weight derived from conjugated dienes, e.g., 1,3-butadiene and a monovinyl-substituted aromatic compound, e.g., styrene, can be laminated with polyalkenes. The disadvantages of these suggestions are self evident.